Extraordinary celestial spiral
66.
This remarkable picture shows one of the most perfect geometrical forms created in space. It captures the
formation of an unusual pre-planetary nebula, known as IRAS 23166+1655, around the star LL Pegasi (also known
as AFGL 3068) in the constellation of Pegasus (the Winged Horse).
The striking picture shows what appears to be a thin spiral pattern of astonishingly regularity winding around the
star, which is itself hidden behind thick dust. The material forming the spiral is moving outwards a speed of about
50 000 km/hour . Astronomers calculate that the shells are each separated by about 800 years.
The spiral is thought to arise because LL Pegasi is a binary system, with the star that is losing material and a
companion star orbiting each other. The spacing between layers in the spiral is expected to directly reflect the
orbital period of the binary, which is indeed estimated to be also about 800 years.
Credit: ESA/NASA & R. Sahai
Stripping
67. away at NGC 4522
Hubble allows astronomers to study an interesting and important phenomenon called ram pressure
stripping that is so powerful, it is capable of mangling galaxies and even halting their star formation.
NGC 4522 is a spectacular example of a spiral galaxy that is cu